From 2e8fd4c5cdeb59ae2bd403aa5069993303e8388e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Fri, 24 Jul 2015 02:31:58 +0200
Subject: [PATCH] Add concatStringsSep as a primop
This fixes the quadratic behaviour of concatStrings/concatStringsSep
in Nixpkgs.
---
src/libexpr/primops.cc | 21 +++++++++++++++++++++
tests/lang/eval-okay-concatstringssep.exp | 1 +
tests/lang/eval-okay-concatstringssep.nix | 8 ++++++++
3 files changed, 30 insertions(+)
create mode 100644 tests/lang/eval-okay-concatstringssep.exp
create mode 100644 tests/lang/eval-okay-concatstringssep.nix
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 7a4aad3cd..c320b4c39 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1514,6 +1514,26 @@ static void prim_match(EvalState & state, const Pos & pos, Value * * args, Value
}
+static void prim_concatStringSep(EvalState & state, const Pos & pos, Value * * args, Value & v)
+{
+ PathSet context;
+
+ auto sep = state.forceString(*args[0], context, pos);
+ state.forceList(*args[1]);
+
+ string res;
+ res.reserve((args[1]->listSize() + 32) * sep.size());
+ bool first = true;
+
+ for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
+ if (first) first = false; else res += sep;
+ res += state.coerceToString(pos, *args[1]->listElems()[n], context);
+ }
+
+ mkString(v, res, context);
+}
+
+
/*************************************************************
* Versions
*************************************************************/
@@ -1720,6 +1740,7 @@ void EvalState::createBaseEnv()
addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
addPrimOp("__hashString", 2, prim_hashString);
addPrimOp("__match", 2, prim_match);
+ addPrimOp("__concatStringsSep", 2, prim_concatStringSep);
// Versions
addPrimOp("__parseDrvName", 1, prim_parseDrvName);
diff --git a/tests/lang/eval-okay-concatstringssep.exp b/tests/lang/eval-okay-concatstringssep.exp
new file mode 100644
index 000000000..93987647f
--- /dev/null
+++ b/tests/lang/eval-okay-concatstringssep.exp
@@ -0,0 +1 @@
+[ "" "foobarxyzzy" "foo, bar, xyzzy" "foo" "" ]
diff --git a/tests/lang/eval-okay-concatstringssep.nix b/tests/lang/eval-okay-concatstringssep.nix
new file mode 100644
index 000000000..adc4c41bd
--- /dev/null
+++ b/tests/lang/eval-okay-concatstringssep.nix
@@ -0,0 +1,8 @@
+with builtins;
+
+[ (concatStringsSep "" [])
+ (concatStringsSep "" ["foo" "bar" "xyzzy"])
+ (concatStringsSep ", " ["foo" "bar" "xyzzy"])
+ (concatStringsSep ", " ["foo"])
+ (concatStringsSep ", " [])
+]
--
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